Display system and method for displaying windows of an operating system to provide a three-dimensional workspace for a computer system

ABSTRACT

The present invention provides a three-dimensional perspective, virtual workspace to window based display systems. The user may activate control buttons to transform a typical two-dimensional window to a three-dimensional perspective, virtual workspace. The transformation to the three-dimensional workspace provides a perspective or sense of depth to the display of the windows containing computer applications. In this manner, a simulated three-dimensional window display environment for the operating system is provided. The operating system utilized in connection with the present invention receives data for storage in a destination rectangle in a frame buffer. The data designated for storage in a destination rectangle is generally given in pixel coordinates. The operating system scales the data&#39;s dimensions to the provide a three-dimensional perspective appearance on the display screen. When a user indicates that a window should be displayed in a particular perspective or size, coordinates representing the window and data contained therein are multiplied by a transformation matrix to yield the specified perspective or size.

FIELD OF THE INVENTION

The present invention relates generally to a display system for managingand manipulating information on a computer display screen operating in awindow display environment, and more particularly, relates to a displaysystem for managing and manipulating the displayed windows of theoperating system to provide a virtual three-dimensional workspace forthe computer system.

BACKGROUND OF THE INVENTION

In a physical environment, such as on a desk or table, an individual mayutilize certain areas for placement of documents for convenient viewing.The surface area on the desk used to support the documents for viewingmay be termed a workspace. Because the physical space on a desk forworking is limited multiple documents may be spread out or arranged insome systematic manner within the workspace. When multiple documentsrequire more surface area than the available area of the workspace,documents may be stacked, within the workspace, with identifyingportions being visible.

In a computer system, the workspace for viewing documents orapplications is the display screen or monitor of the computer system.The operating system of the computer system generally manages orcontrols the documents or applications displayed on the monitor. Earlycomputer systems displayed only one document or application on thedisplay screen at a time, therefore limiting the effective computerworkspace. In order to switch among multiple applications or documents,the user had to close the application or document being displayed andopen a different application or document. Such a computer system wascumbersome. With the introduction of multi-tasking and graphicalinterfaces, the display screen was divided into multiple portionsgenerally referred to as windows. A window is a portion of the displayscreen that may contain its own document or message.

In window-based programs, the screen can be divided into severalwindows, each of which has its own boundaries and can contain adifferent document. The operating system controls these speciallydelineated window areas of the screen. Each window can actindependently, as if it were a virtual display device. In window displayenvironments, the windows may be resized and moved around on the displayscreen. Thus, with the advent of window-based programs, the computerscreen workspace became more flexible. The ability to resize and movewindows as well as to overlay or stack windows on top of each otheressentially provided the same type of workspace available on a physicaltwo-dimensional tabletop workspace except on a smaller scale.

Present day computer systems often employ "object-oriented" displayswith windows, icons, pictures, text, pop-up or drop-down menus, dialogboxes, and other graphical items or objects in what is known as a"Graphical User Interface" ("GUI"). In such systems, variouscombinations of graphical items or objects are utilized to conveyinformation to users via the monitor or display. Users interact with thecomputer system by activating graphical items or objects on the display.The graphical items or objects are often activated by pointing at themwith a cursor controlled by a mouse or pen and clicking a control buttonon the mouse or pen.

An example of a computer graphical user interface that uses icons andwindows is the Microsoft "WINDOWS"™ operating system manufactured andsold by the assignee of the present invention, Microsoft Corporation.Common user interfaces such as those found in the Microsoft "WINDOWS"operating system and other GUI-based computer systems typically rely ona keyboard and a pointing device with buttons such as a mouse ortrackball for user interaction. The user points to a location on thescreen where an action is desired, and invokes a command by pressing abutton on the pointing device or entering a keyboard command.

Just as a physical desktop table can become cluttered when multipledocuments are being viewed, a computer screen workspace can becomecluttered when multiple documents are displayed in multiple windows.With limited working space or viewing area on a computer screen, thecomputer screen workspace can quickly become cluttered if severalapplications or windows are opened at the same time. A number oftechniques have been used for overcoming the small-screen problempresented when using computer displays.

Four general categories of computer screen workspace enhancementtechniques are: (1) alternating screen uses, (2) distorted views, (3)large virtual workspaces, and (4) multiple virtual workspaces.Alternating-screen use is similar to windows in that the user can switchor change the allocation of screen space from one application toanother. Some early alternating screens use techniques only allowed oneapplication to be visible on a screen at a time. With distorted views,documents or applications appearing on the screen may be distorted tosmall icons. Here, applications are reduced to small pictures or iconsthat remind the user of the original window. Overlapping or stackedwindows may also be considered a distorting technique. As noted above,when many windows overlap the appearance on a display screen may becomecluttered.

With large virtual workspaces, the set of objects, the documents, orapplications are organized as a large virtual workspace which cannot allbe viewed on a display screen simultaneously. In one exampleapplication, the data is arranged in two dimensions, and the user hasthree screens, one for an overview of the whole space, one for adetailed view of some portion of the space, and one touch screen forcontrol. Head-mounted displays, which monitor user head and bodymovements to give the user a complete simulated three-dimensional spaceview, are forms of large virtual workspaces. A problem with a singlelarge workspace is that only a limited number of things can be adjacentto any object. The space required for the objects and their shapesconstrains the manner in which the space may be arranged and how denselypacked documents or data can be presented. Multiple virtual workspacesprovide geometrically-oriented workspaces linked together in which aproject may contain a number of views and, when active, covers theentire screen. For example, when a user maneuvers close enough to aport, the user is swept into another workspace or subworkspace.

The above techniques are examples of display systems which try toovercome the limited workspace inherent with computers that displaymultiple applications or documents on a two-dimensional display screen.However, these display systems do not provide a method for displayingmultiple applications presented by an operating system in threedimensions. Thus, there is a need in the art for a display system whichprovides an enhanced system for displaying multiple applications orwindows as simulated three-dimensional objects on a computer displayscreen.

SUMMARY OF THE INVENTION

Generally described, the present invention provides a three-dimensionalvirtual workspace for a window based display system. The display systemof the present invention is an isometric display system for an operatingsystem. The isometric display system provides a display with monoculardepth cues by making automatic sizing and geometric transformations ontwo dimensional rectangles that define traditional windows.

The isometric display system performs geometric transformationoperations on rectangular windows to convey the impression to the userthat the windows are positioned in a three-dimensional space. Theimpression of depth and of working in a three-dimensional space arecreated by transforming two-dimensional windows to appear as if thetwo-dimensional windows are embedded at orientations and positions in athree-dimensional isomeric space. The isometric display system respondsto user activation of control buttons by transforming the shape andorientation of windows consistent with the defined three-dimensionalspace.

More particularly described, the present invention provides a method ofutilizing left, right, front, back, upper, and lower planes. Theseplanes define a polyhedron and these planes may be referred to as"boundary planes". The polyhedron surrounds a three-dimensional spaceused by the isometric display system to manage the configuration andposition of windows containing data from applications. The boundaryplanes of the virtual space are preferably organized into a rectangularprism defining left, right, front, and back walls, a ceiling, and afloor of a four-sided room as seen when viewing the room from theoutside through a selected wall or user viewpoint.

Boundary planes may be explicitly displayed with shaded solid surfacesor simply as lines defining the intersection of planes. However, theplanes are preferably not visible. The front boundary plane is typicallyassumed to be the front surface of the display, closer to the user thanthe rear boundary plane. When the boundary planes are made visible, theleft and right walls, and the ceiling and floor defined by the planesnarrow in dimension as viewed from the front to back of the spacedefined on the display screen. Windows may be oriented and displayed inthe boundary planes.

Windows oriented in the front boundary plane are displayed withouttransformation, and appear as standard rectangular window, as intraditional windowing systems. When a transformation command is enteredby a user or from a program, a window is transformed and moved to theselected plane of the display system to create the perception of depth.A window selected for display on the rear plane appears as a rectangularwindow that has been pushed back in the three-dimensional space. Awindow designated for another plane is rotated 90 degrees and appearspushed flat against the designated plane.

For generating the illusion of moving the windows away from the user inthe three-dimensional space, the display system decreases the size ofthe window and its contents equivalently in the x and y dimensions, as afunction of its assigned distance from the user in the three-dimensionalspace. The display system moves the window towards the center of thespace based on the relative distance between the front and the rearboundary planes. When a window on the front plane is moved toward therear plane, the window can snap immediately to the rear plane and appearin a reduced size or the window may move incrementally to anintermediate plane or planes between the front and rear plane.Additionally, a window moved toward the rear plane may continuouslydecrease in size as the window approaches the rear plane.

User or system accessible controls are used for displaying or hanging anuntransformed window on a left, right, rear, upper, or lower boundaryplane. For example, when a user invokes the "perspective-transformright" command, the display system applies a perspective transform onthe rectangular window and its contents and redisplays the rectangularwindow as an appropriately sized and shaped trapezoid. The window asdisplayed appears to be rotated 90 degrees form its initial position andappears to be repositioned to fit within the right boundary plane. Whena window is moved along or to a boundary plane, the window may becontinuously resized based on its position in the three-dimensionalspace or the window may snap to predefined locations.

When the intended destination of a selected window is a boundary planealready containing a transformed window, the selected window is placedon an adjacent plane to the boundary plane that is closest to theboundary plane. Adjacent planes refer to planes that are parallel (inthe three-dimensional space) to the boundary plane but that arepositioned at selected increments away from the boundary plane along thenormal vector from the plane towards the center of the virtual space.Windows selected for display on a designated plane are displayed on theclosest available adjacent plane. This provides an ordering of displayedwindows from the center of the three-dimensional space to the boundaryplane for all transformed windows on the boundary plane. The contents ofdisplayed windows may be generally viewed in full when the windows arehung on different planes. Also, the windows may have focus or beoperated on when displayed or hung on a plane.

Three primary controls may be used to position a window hung on a plane:push back, perspective-transform right, and perspective-transform left.Push back causes a window to be transformed or pushed to the foregroundor background of the display system. Perspective-transform rightgenerally causes a window to be displayed on the right plane andperspective-transform left generally causes a window to be displayed onthe left plane. Alternatively, a single transformation control fortransforming windows to the various planes may be implemented. Uponselection of the single transformation control, the display systemprovides a pointer to a selected plane. The pointer may be operative topoint to a plurality of predefined planes. The pointer may be adirection arrow. Generally, the pointer is provided when the cursorcontrol is activated or pulled in the direction of a predefined planewhile the cursor is positioned on the transformation control. The usermay release the cursor control to initiate the transfer ortransformation of the window.

The operating system utilized in connection with the present inventionreceives data from an operating system, an application or other sourcefor display in a window. The data may be stored by the operating systemin the same manner as in rectangular windows. Before displaying the datain a window on the display screen, the operating system scales the shapeof the window to fit the selected plane and the data presented in thewindow. The scaling of the window's shape and the scaling of the datapresented in pixel coordinates within the window creates athree-dimensional appearance on the display screen.

Transformation matrices may be used in the operating system to transformor scale a window to the selected plane. When a user indicates that awindow should be displayed on a particular plane, both the coordinatesof the window and data contained in the window are multiplied by atransformation matrix to fit the window in the area defined by theselected plane and transform the data content of the window. Bytransforming the window and data, depth perception for the window iscreated.

The present invention may also provide a method of dynamically sizingthe cursor as a function of the location of the cursor on the displayscreen. The present invention may determine the position of the cursoron the display screen, and resize the cursor based upon the location ofthe cursor on the display screen. The size of the cursor may change whenthe cursor crosses over a border of a window. The size of the cursor mayspecifically change relative to the cursor location on a window toreflect the depth of that location in three-dimensional space defined bythe transformed windows. This serves to give feedback to the user aboutthe location of the cursor in three-dimensional space by generating theperception that the cursor resides on or jumps to planes defined by thetransformed windows.

Thus, it is an object of the present invention to provide an enhanceddisplay system for displaying applications and documents in a computersystem.

It is another object of the present invention to manipulate thedisplayed windows to create a virtual three-dimensional workspace on themonitor of the computer system.

It is another object of the present invention to provide a displaysystem for simultaneously displaying multiple applications and objectsmanaged by the operating system as a consistent three-dimensionaloperating environment.

It is another object of the present invention to transform the shapesand contents of a displayed window to create a perspective view of thewindow and its contents.

It is another object of the present invention to partition the displayscreen of a display monitor into multiple planes for displaying selectedwindows in a preselected form.

It is another object of the present invention to dynamically size acursor relative to the location of the cursor on the display screen.

These and other objects, features, and advantages of the presentinvention will become apparent from reading the following description inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the basic components of a computer systemused in connection with the preferred embodiment of the presentinvention.

FIG. 2 is a block diagram showing the basic components of the computersystem used in connection with the preferred embodiment of the presentinvention.

FIG. 3 illustrates a detailed view of the display screen generated inaccordance with the present invention.

FIG. 4a, 4b, and 4c illustrate a manipulation of displayed windows inaccordance with the present invention.

FIG. 5a, 5b, and 5c illustrate another manipulation of displayed windowsin accordance with the present invention.

FIG. 6a, 6b, and 6c illustrate another manipulation of displayed windowsin accordance with the present invention.

FIG. 7a, 7b, 7c, and 7d illustrate an alternate embodiment of a controlmechanism for manipulation of displayed windows in accordance with thepresent invention.

FIG. 8a, 8b, 8c, and 8d illustrate an alternate embodiment of a controlmechanism for manipulation of displayed windows in accordance with thepresent invention.

FIG. 9a and 9b illustrate an alternate embodiment of a control mechanismfor manipulation of displayed windows in accordance with the presentinvention.

FIG. 10a and 10b illustrate alternate embodiment of a control mechanismfor manipulation of displayed windows in accordance with the presentinvention.

FIG. 11 illustrates lines demarcating areas for display of windows inaccordance with the preferred embodiment of the present invention.

FIG. 12 illustrates a non-planar bounding surface for defining athree-dimensional workspace.

FIG. 13 illustrates multiple isometric spaces constructed according toan embodiment of the invention.

FIG. 14 illustrates an alternate view of the multiple isometric spaces.

FIG. 15 illustrates the method of dynamically sizing the cursor of thepresent invention.

FIGS. 16a and 16b are flow diagrams showing the steps implemented in thepreferred embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals illustrate likeelements throughout the several views, FIG. 1 illustrates the basiccomponents of a computer system 10 used in connection with the preferredembodiment of the present invention. FIG. 1 illustrates a graphical userinterface 12 on a computer display screen 15 of a display monitor 14 ofthe computer system 10. The graphical user interface of the displaysystem is preferably implemented as part of the operating system toprovide a three-dimensional environment for displaying and managing thewindow objects of the operating system. The present invention enablescutting and pasting, moving objects, and other functions as generallyperformed by an operating system while providing visual depth cuesdisplayed by the operating system consistent with the orientation andposition of the object within predefined boundaries defining a space forproviding the depth cues. Additionally, sounds such as beeps and warningsignals, generally associated with the interaction of a user with acomputer system, may appear, using stereo sound, to emanate from thewindow upon which a user is operating in the three-dimensional space. Byvarying the level of the sound and/or direction from which the soundsemanates, the sound may appear to emanate from a selected window.Although the present invention is described in conjunction with aconventional desktop computer, it will be appreciated that the presentinvention may be utilized in other types of computer systems that use awindow based display system. The graphical user interface system 12 isimplemented with a computer 16 connected to the display monitor 14. Thecomputer 16 receives input data from a conventional keyboard 20 via aninput line 18. Cursor keys on the keyboard 20, a mouse 21, trackball, orother pointing device may be used to move a cursor 23 on the displayscreen 15 for selection of various options. It should be appreciated bythose skilled in the art that text entry or command input also may beaccomplished by using a touch-sensitive pad or handwriting recognitiondevice in conjunction with software for recognizing the correspondinginput signals as selection signals.

Referring to FIG. 2, the hardware components of the computer 16 areillustrated. For simplicity of the drawings, many components of astandard computer system have not been illustrated such as addressbuffers, memory buffers and other standard control circuits becausethese elements are well known and illustrated in the prior art and arenot necessary for the understanding of the present invention. A computerprogram used to implement the various steps of the present invention isgenerally located in the memory unit 20, and the processes of thepresent invention are carried out through the use of a centralprocessing unit (CPU) 22. Those skilled in the art will appreciate thatthe memory unit 20 is representative of both read-only memory and randomaccess memory. The CPU 22 is typically implemented as a single-chipmicroprocessor, such as the models 80386 or 80486 that are availablefrom Intel Corporation, Santa Clara, Calif. The CPU 22, in combinationwith computer software, such as an operating system 25 and applicationprograms 27, controls the operations of the computer system 10. Theoperating system software 25, in conjunction with application programs27, controls the allocation and usage of hardware and software resourcessuch as memory, CPU time, disk space, and peripheral devices. It shouldbe appreciated that many window based operating systems exist such asMicrosoft "WINDOWS", a UNIX (e.g. X-windows) operating system, or aMacintosh operating system. The display routines are encoded in agraphical user interface display layer in the operating system. Thesystem bus 24 supports communications of control, address, and datasignals between the CPU 22 and the remaining components of the computersystem 10. The memory unit 20 and the CPU 22 are connected by a computersystem bus 24 designed to provide an electrical interface betweencomputer system components. The processes implemented by the CPU 22 maybe communicated as electrical signals along the computer system bus 24to an input/output device 26, such as display monitor 14. The displaymonitor 14 provides a visual display of computer generated graphicsoriginating from the processes implemented by the CPU 22.

In this detailed description, numerous details are provided such ascomputer display system elements, object definitions, display formats,sample data, etc., in order to provide an understanding of theinvention. However, those skilled in the art will understand that thepresent invention may be practiced without the specific details.Well-known circuits, programming methodologies, and structures areutilized in the present invention but are not described in detail inorder not to obscure the present invention.

Certain of the descriptions which follow are presented in terms ofdisplay images, processes, and symbolic representations of operations ofdata bits within the computer's memory. As will be known to thoseskilled in the programming arts, these process descriptions, classdescriptions, messages, notification descriptions, and graphic displaysare the means used by those skilled in the art of computer programmingand computer construction to convey teachings and discoveries to othersskilled in the art.

For purposes of this discussion, a process or method is generally asequence of computer-executed steps leading to a desired result. Thesesteps require physical manipulations of physical quantities. Usually,though not necessarily, these quantities take the form of electrical,magnetic, or optical signals that are capable of being stored,transferred, combined, compared, or otherwise manipulated. It isconventional for those skilled in the art to refer to these signals asbits, data, values, elements, symbols, characters, images, terms,numbers, or the like. It should be kept in mind, however, that these andsimilar terms should be associated with appropriate physical quantitiesinside the computer and that these are merely convenient labels appliedto these physical quantities that exist within the computer.

It should also be understood that manipulations within the computer areoften referred to in terms such as adding, comparing, moving, etc.,which are often associated with mental operations performed by a humanoperator. It must be understood that involvement of a human operator isnot necessary in the present invention because the operations describedherein are machine operations performed in conjunction with a humanoperator or user that interacts with the computer. The machines used forperforming the operation of the present invention include generalpurpose digital computers or other similar computing devices.

The present invention relates to methods, steps, or operations for acomputer which processes electrical or other physical signals togenerate desired physical signals and display results and interactions.As illustrated in FIG. 1, the present invention also relates toapparatus 10 for performing these operations. This apparatus 10 may beespecially constructed for the described purposes.

Furthermore, it should be understood that the programs, processes,objects, etc., described herein are not related or limited to anyparticular computer or apparatus. Rather, various types of generalpurpose machines may be used with programs constructed in accordancewith the teachings herein. Similarly, it may prove advantageous toconstruct specialized apparatus to perform the method steps describedherein by way of dedicated computer systems with hard-wired logic orprograms stored in nonvolatile memory such as read only memory.

Referring again to FIG. 1, the programming techniques and manner ofhandling windows in a computer system will be discussed. Those skilledin the art will understand and appreciate that operating systems fordisplaying and utilizing windows may be implemented by usingobject-oriented programming languages and techniques. Object-orientedprogramming techniques are utilized by those skilled in the art ofcomputer programming because they provide a powerful way to view theinteraction of a user with a computer system. For example, oneparticular "object" that people often work with on computer screens iscalled a window. Referring to FIG. 1, a window 30, as discussed above,is a rectangular area on the display screen 15 that is used to displayinformation or receive commands or data from the user. The displayscreen 15 itself may be considered a window into the computer 16. Thewindow 30 receives user input from a keyboard 20, mouse 21, or pen, anddisplays graphical output upon which a user may interact. The displayscreen 15 thereby serves as the workspace for the computer. A computerprogram is responsible for generating the window 30 and for respondingto user interactions with the window 30. The window 30 often containsthe computer program's title bar 32 across the top of the window 30,menus, sizing borders, and perhaps other objects.

The window 30 may contain additional, smaller windows called "childwindows", which are subspecies or subclasses of windows. Child windowsmay take the form of push buttons, radio buttons, check boxes, textentry fields, list boxes, and scroll bars, and the like. These objectswhen displayed on the computer screen may be pressed or clicked orscrolled. A user sees a window as an object on the screen, and interactsdirectly with the object by pushing buttons 34, or scrolling a scrollbar, or tapping a handle displayed in the window 30. Buttons 34 maycontrol a function for the particular window.

A window generated by a computer program receives user input in the formof messages to the window. The messages are generated by an eventhandling routine that is responsive to user input such as tapping,clicking, or dragging a cursor with a stylus or mouse.

The following is a brief example of an object-oriented programmingmethodology for resizing a window utilized in the Microsoft "WINDOWS"graphical user interface operating system. Consider a word processorapplication computer program that displays text in a window. The windowmay include a "size box", which is a control located at the lowerright-hand corner of the window. If selected and dragged, the size boxcauses the size of the window on the display screen to become larger orsmaller. If the program's window is resized, the word processing programapplication program will reformat and move the text on the displayscreen to fit within the window when the window is resized.

The computer's operating system program generally handles the details ofresizing the window, and the application program running under controlof the operating system program responds to the system function ofresizing the window. The word processing program "knows" when its windowis resized because a message is passed to it indicating a resizingoperation, and the application program responds by repositioning thetext within the available window. In the "WINDOWS" operating system,when a user resizes a window, the operating system sends a message tothe application program indicating the new window size. The program thenadjusts the contents of its window to reflect the new size.

The passing of a message to a program is tantamount to making a call toa function within the program. Such a function call can be made to theoperating system or to an application program. Those skilled in the artwill understand that such mechanisms are how a program opens a diskfile, for example, or scrolls text from an area that is "off screen"into view within the window. An operating system may make calls to aprogram by passing it messages, in a similar manner that the applicationprogram makes a call to the operating system.

Every window object that a program creates has an associated windowprocedure (also called a "method"). This window procedure or method is afunction that could be either in the program itself or in a linkedlibrary of appropriate routines that can be executed upon a call. The"WINDOWS" operating system sends a message to a window by calling awindow procedure. The window procedure does processing based on themessage passed to it and then returns control to the operating system,possibly with a "notification" or other response. (A "notification" ismerely a message passed back to a calling program, and usually indicatesstatus information or the results of an operation.)

A window displayed on a display screen is based on what is known as a"window class" of objects. The window class of objects identifies aparticular procedure that processes messages passed to that window. Theuse of a window class allows multiple windows to be based on the samewindow class, and thus use the same window procedure. For example,control buttons in programs that utilize the "WINDOWS" operating systemare based on the same window class. A window class is associated with awindow procedure that processes messages to all button windows.

In object-oriented programming, an "object" is a combination of computerprogram code and data. A window is a type of object. The computerprogram code carries out tasks associated with the object. The data isthe information retained by the window procedure and informationretained by the "WINDOWS" operating system, for each window or windowclass that exists.

A window procedure processes messages to the window. Often thesemessages inform a window of a user input from a keyboard, mouse, or pen.This is how a child window that is a button "knows" that it is being"pressed," or an icon "knows" that it is being dragged. Other messagestell a window when it is being resized or when the surface of a windowneeds to be repainted on the monitor.

When a program begins execution in such an operating system as the"WINDOWS" operating system, the operating system creates a "messagequeue" for the program. This message queue stores messages to all thevarious windows a program may create. The program includes a portion ofprogram code called the "message loop" to retrieve the messages from thequeue and dispatch them to the appropriate window procedure. Othermessages may be sent directly to a window procedure without being placedin the message queue.

Three-Dimensional Window Operation and Control

Referring to FIG. 3, a more detailed view of the graphical userinterface 12 of the display screen 15 of the present invention is shown.The graphical user interface 12 provides depth cues in a manner to yielda three-dimensional view of the windows and/or objects displayed on thedisplay screen 15. A window is considered to be transformed whenthree-dimensional depth cues are provided to the window. Thus, asimulated three-dimensional display of the windows is provided. Byproviding three-dimensional graphics to the windows/objects created andmanaged by an operating system, the computer workspace is effectivelyenlarged for a standard graphical user interface consisting of windows,icons, menus, and pointer (WIMP). The display screen may be consideredto have an x, y, z coordinate system with an x-axis 310, a y-axis 312,and a z-axis 314. The three-dimensional virtual workspace displays thewindows and objects of the operating system so that the windows andobjects appear to project along the z-axis 314 into the display screen15. Each displayed window has its own set of buttons and controls as inconventional window environments including transformed windows.

The display or positioning of the windows on the display screen 15 iswithin predefined boundaries that may be considered a space or openroom. The open room can be viewed from the outside, with the room havingfront, back, top, bottom, left, and right walls. As used herein, "walls"of a three-dimension room space may be referred to as planes. The frontplane 38 shown containing the window 40 provides a view which is similarto a window as typically presented in conventional windowingenvironments in two dimensions. In conventional windowing environments,the windows and data are shown on a single front or forward twodimensional plane. However, unlike conventional window systems, a backplane 44 and other planes may be utilized to display a window 46 asillustrated.

The back plane 44 displays a window that is generally the same shape(rectangular) as a window on the front plane 38 except that the window46 displayed on the back plane 44 is zoomed back or set at a distance(along the z-axis 314) from the front plane 38. Thus, the windowsappearing or "hanging" on the back plane 44 have smaller dimensions andthus appear farther away than the windows appearing on the front plane38. In addition to the window 46 appearing smaller than the window 40 onthe front plane 38, the text within the window 46 on the back plane isalso reduced in scale to further give the appearance of distance alongthe z-axis 314.

As noted above, the left and right planes 50 and 56 are analogous to thesides or the walls of a room or box. As illustrated, a window 58 may bepositioned on or "hung" on the right plane 56. Similarly, a window 52may be hung on the left plane 50. Windows hung on either the left plane50 or the right plane 56 are considered to be in "perspective." When awindow is in perspective, the edge 53 of the window that is farthestaway from the user's view, as looking along the z-axis 314 into thedisplay screen 15, is smaller than the edge 55 that appears closer tothe user. Although not illustrated with windows displayed thereon inFIG. 3, bottom or floor planes 106, and top or ceiling planes 102 may beused for hanging windows at the bottom or top of the screen,respectively. Windows appearing at the top or bottom of the displayscreen 15 would likewise be displayed in perspective at the bottom ortop of the screen, similar to the windows 52 and 58 displayed on theleft plane 50 and the right plane 56, respectively.

When an application program is initially opened, a window is created andattached to the front plane 38. The window will remain on the frontplane 38 until the user positions the window on another plane by use ofa transfer or transformation control, such as the perspective-transformleft button 66, perspective-transform right button 68, or pushbackbutton 64. The current plane will become part of the profile informationfor the application so subsequent invocations of the program will resultin a window being created and attached to the plane that the window wasattached to when the application was last shut down. For example, if themain window of an application is attached to the left plane 56, when theuser closes the application using the exit command on the file menu ofthe application, the next time the user runs the application, theapplication's main window will appear on the left plane 56 because thatis where the main window was when the application was terminated.

When a user resizes a window or perspective-transforms a window inaccordance with the present invention, the computer application handlesthe resizing operation as the program would in a conventional windowenvironment. However, the operating system provides the appropriatescaling for the shape, size, and contents of the window to fit on theappropriate plane. Thus, no specialized programming is required forcomputer applications designed to operate in conventional window-basedoperating systems.

In conventional window display systems, the operating system specifies adestination rectangle which specifies the location in the frame bufferfor displaying the window containing the computer application data. Thedestination rectangle is generally specified in pixel coordinates. Theoperating system utilized in connection with the present inventionreceives data that is created to be stored in a destination rectangle ina frame buffer then scales the data to dimensions that provide adestination area yielding a three-dimensional depth or perspectiveappearance on the display screen. This destination area is given inpixel coordinates.

When the operating system and CPU detect that one of the control buttonshas been selected, the operating system notifies the appropriate windowobject, and it then uses a series of notifications (a) to release itselffrom the plane that it is currently attached to and (b) to attach itselfto a different plane based on the control that was selected.Transformation matrices, as known to those skilled in the art, areapplied during rendering of the image. The transformation matrices areapplied to the drawing commands that an object sends to the graphicsengine of the computer system. The matrices are standard 4×4transformation matrices known to those skilled in the art.

With continuing reference to FIG. 3, the control buttons 34 forcontrolling the positions of the display windows on the various planesof the display system are shown. A system menu button 60, a title bar62, a push back button 64, a perspective-transform left button 66, and aperspective-transform right button 68 are shown along the top of window40. The same control buttons are displayed in the same position on thewindow 46 appearing on the back plane 44 and in a left-to-rightarrangement as illustrated on the window 40. When a window is attachedor hung on the left plane 50 or right plane 56, the controls 34 arearranged top to bottom as illustrated on windows 58 and 52. Also, thetitle bar 62 is realigned so that when the title bar 62 is attached toeither the right plane 56 or the left plane 50, the text runs from topto bottom. The function of the controls of the display system are asfollows.

The system menu accessed by the system menu button may provide a menuaccess to the functionality provided by the pushback button 64,perspective-transform left button 66, and perspective-transform rightbutton 68 as well as access to functions that move and resize a window.The functionality of moving and resizing is the same as the system menuin the current Microsoft Windows GUI. The title bar 62 contains thetextual representation of the name of the "owning" window. The term"owning" generally means the object containing a specified item or theobject to which the item pertains. The name appearing in the title bar62 can be changed by the operating system program by means of a messageto the owning window when a user makes the appropriate change. The textis re-oriented, such as left-to-right or top-to-bottom, based upon theplane on which the window is displayed.

By selecting the push back button 64 of a particular window, the windowis displayed or moved to either the front plane 38 or back plane 44depending upon which of the planes the window is currently located. Ifthe push back button 64 is selected and the window was on front plane38, then the window is zoomed backward and attached to the back plane44. If the window is currently located on the back plane 44 when thepush back button 64 is selected, then the window is zoomed forward andattached to the front plane 38. Similarly, if the push back button 64 isselected on a window 58 that is located on a side plane, the window ispushed back to either the front plane 38 or the back plane 44 dependingon whether the window was previously attached to the front plane 38 orthe back plane 44. When the push back button 64 is selected and if thewindow 58 was previously attached to the front plane 38, then the window58 is pushed back to the back plane 44 and vice versa. When the pushback button is selected and if the window 52 was previously attached tothe back plane 44, then the window 52 is pushed back to the front plane38 and vice versa.

When the perspective-transform left button 66 is selected for aparticular window, the window is placed on the left plane. If the windowis currently attached to either the front plane 38 or the back plane 44,then the operating system causes the window to be removed from thecurrent plane and displayed on the left plane. When a window is selectedto be transferred to the left plane 50, the current plane containing thewindow is saved as the last saved plane for that selected window to bereferenced when the perspective-transform controls are subsequentlyselected for the window. If the window is currently attached to the leftplane 50 when the perspective-transform left button is selected, theoperating system 25 removes the current window from the left plane andattaches the current window to the last saved plane. For example, when awindow is attached to the front plane and the perspective-transform leftbutton is selected, the window is attached to the left plane, and thefront plane position is saved as the last saved plane. Selecting eitherthe perspective-transform left or perspective-transform right button onthis window will result in the window being detached from the left planeand returned to the front plane. If the window had been attached to theback plane prior to the perspective-transform left button beingselected, the window would be returned to the back plane. The systemdoes not save the left plane position when a window is removed from theleft plane because the perspective-transform left button positions thewindow on the left plane.

When the perspective-transform right button 68 is selected for aparticular window, the window will be placed on the right plane. If thewindow is currently attached to either the front plane 38 or the backplane 44, then the operating system causes the window to be removed fromthe current plane and displayed on the right plane. When a window isselected to be transferred to the right plane 56, the current planecontaining the window is saved as the last saved plane for that selectedwindow to be referenced when the perspective-transform controls aresubsequently selected for the owning window. If the window is currentlyattached to the right plane 56 when the perspective-transform rightbutton 68 is selected, the operating system 25 removes the currentwindow from the right plane and attaches the current window to the lastsaved plane. For example, when a window is attached to the front plane38 and the perspective-transform right button 68 is selected, the windowis attached to the right plane, and the front plane position is saved asthe last saved plane. Selecting either the perspective-transform left orperspective-transform right button on this window will result in thewindow being detached from the right plane 56 and returned to the frontplane 38. If the window had been attached to the back plane prior to theperspective-transform right button 68 being selected, the window wouldbe returned to the back plane. The system does not save the right planeposition when a window is removed from the right plane because theperspective-transform right button positions the window on the rightplane.

Basic controls 60, 64, 66, and 68 utilized with the present inventionare invoked with a mouse selection device in the same manner as thecontrols are selected in a conventional window environment. Also, thewindows operating within a system of the present invention may be"dragged" to new positions as in conventional window applications. Byclicking and holding the primary mouse button while the cursor 23 is inthe title bar of a window, the window can be dragged to a new location.The window may be dragged to a new location when it is on any of theplanes. The window movement and size may be limited to the extents ofthe defined planes.

Referring again to FIG. 1, windows may be stacked behind one another asillustrated with windows 70 and 72. Window 72 appears behind window 70.Because these windows are stacked, an order for these windows isestablished. The ordering of the windows is termed the "z" position. Alist, termed the z-order list, indicates the order or spacing of windowsas the windows appear on a plane of the display screen. A basic stackingprocedure places a window into the first available slot in the z-orderlist. When placing a window in the first available slot, a newlyperspective-transformed window may disappear behind windows that arealready attached to the plane rather than appearing in front of thewindows that are currently displayed on the plane. For example, when theintended destination of a selected window is to a boundary plane alreadycontaining a transformed window, the selected window is placed on theadjacent plane to the boundary plane that is closest to the boundaryplane, such as plane 71 containing window 72. Adjacent planes refer toplanes that are parallel (in the three-dimensional space) to theboundary plane but that are positioned at selected increments away fromthe boundary plane along the normal vector from the plane towards thecenter of the virtual space. Windows selected for display on adesignated plane are displayed respectively to the closest availableadjacent plane. This provides an ordering from the center of thethree-dimensional space to the boundary plane for all transformedwindows on the boundary plane. When placing multiple windows on the leftand right planes, the windows are preferably cascaded slightly down thewall and slightly toward the user. The contents of displayed windows maybe generally viewed in full when the windows are hung on differentplanes. Also, the windows may have focus or be operated on whendisplayed or hung on a plane.

Each plane in the system allocates an array to contain pointers towindows. This array is initialized so that all of the storage locationsare set to zero. When a new window is attached to a plane the array ofwindow pointers is searched and advancing until the first slot in thearray that is zero is found. Once an empty position is found in thearray, the new window pointer is stored at the location. When a windowis detached from a plane, the location in the array that contained thepointer to the window is set to zero. When a plane is notified that itneeds to paint, it iterates through its window pointer array starting atzero. The plane has a member variable that is the number of windows thatare currently attached to the plane. The painting loop terminates whenit either: (a) reaches the end of the array; or (b) determines that ithas painted all of the windows that are currently attached to the planeby incrementing a local variable every time that it finds a window inthe array and comparing this local variable to the member variable thatis the count of the windows currently attached to the plane. It is to beappreciated by those skilled in the art that the specific z-position ofa perspective-transformed window may include various ordering schemesknown by those skilled in the art.

Referring to FIG. 4A, 4B, and 4C, the operation of the push back button64 as applied to a window is illustrated. Referring to FIG. 4A, a window410 is shown displayed on the front plane 38. When the push back button64 is selected within the window 410 by the cursor 23 as shown, thewindow 410 and its data content 415 is transformed or moved to the backplane 44 as illustrated in FIG. 4B. After the push back selection wasinitiated in FIG. 4A, the final position of the window 410 is shown inFIG. 4C. The window 410 shown in FIG. 4C has been fully zoomed backward(set at a distance along the z-axis) to the background where the window410 and its contents 415 have been rescaled to appear at distance fromthe front plane 38.

Referring to FIGS. 5A, 5B, and 5C, the operation of theperspective-transform right button 68 is illustrated. FIG. 5A shows awindow 510 displayed on the back plane 44. When theperspective-transform right button 68 is selected within the window 510by the cursor 23 as directed by the user, the window 510 is transformedor moved to the right plane 56 as illustrated in FIG. 5B. After theperspective-transform right selection was initiated in FIG. 5A, thefinal position of the window 510 is shown in FIG. 5C. The window 510 andits data content 515 shown in FIG. 5C has been fully transformed to theright plane 56 and given a shape that creates the appearance of aperspective rendering, with the left side of the window 510 narrowing asit approaches a selected point or the center point of the display screen15 as the distance along the z-axis increases away from the user.

Referring to FIGS. 6A, 6B, and 6C, the operation of aperspective-transform below button 601 is illustrated. FIG. 6A shows awindow 610 displayed on the plane 38. When the perspective-transformbelow button 601 is selected within the window 610 by the cursor 23 asdirected by the user, the window 610 is transformed or moved to thebottom plane 106 as illustrated in FIG. 6B. After theperspective-transform below selection was initiated in FIG. 6A, thefinal position of the window 610 is shown in FIG. 6C. The window 610 andits data content 615 shown in FIG. 6C has been fully transformed to thebottom plane 106 and given a shape that creates the appearance of aperspective rendering with the far side of the window 610 narrowing asit approaches a selected or center point of the display screen 15 as thedistance along the z-axis increases.

The push back button 64, the perspective-transform left button 66, theperspective-transform right button 68, and the perspective-transformbelow button 601 may be used to transform a nontransformed window into aperspective transformed window or converting a perspective transformedwindow into a nontransformed window by selecting any one of theindividual controls. An alternative method that utilizes a one buttoncontrol process for transforming the windows to the multiple viewswithin the operating system. The one button control for determining theposition of windows on the various walls or planes is discussed inconnection with FIGS. 7A-10C. The one button control discussed in FIGS.7A-10C utilizes a click-and-drag type functionality to designate awindow to be transformed.

Referring to FIGS. 7A-10B, the operation of a single multiple controlwindow transform button 710 is illustrated. A user may guide or place acursor 23 on the window transform button 710 on the tool bar of thenontransformed window 722. A user may then press the selection mechanismof the cursor control, such as a control button on a mouse, and hold themouse control button down and drag it in the direction of the plane onwhich the user wants the window displayed. As the window transformbutton 710 is dragged, an arrow is displayed in the direction of a dragmotion indicated by the user. By displaying the direction arrow, theuser is provided with feedback or given an indication of the computer'sinterpretation of the user's selection. If the user agrees with oraccepts the plane selection indicated by the direction arrow generatedthat points in a direction of the plane on which the window will bedisplayed, the user may release the mouse control button when the planeselection arrow is displayed. The window will then be displayed on theplane indicated by the selection arrow. The window appears to "fling" tothe plane or wall pointed to by the plane direction arrow. By clickingon the window transform button 710 in a window that has already beenperspective transformed, the window is transformed back to a standardwindow and is displayed on the front plane.

Referring to FIGS. 7A, 7B, 7C, and 7D, the operation of the singlewindow transform button 710 is illustrated. The example of FIGS. 7A, 7B,7C, and 7D shows the operation of the window transform button 710 when apushback or zoom out operation is selected by a user. Referring to FIG.7A, the cursor 23 is shown positioned on the window transform button710. The user has selected the zoom out function of the window transformbutton 710. The user makes the selection by positioning the cursor 23 onthe window transform button 710 and by clicking on the window transformbutton 710 and dragging the cursor 23 upwards in the direction of theback plane 44 as indicated by the plane direction arrow 730. Thedirection indicated by the plane direction arrow 730 points toward thezoom out or back plane 44 position. Thus, the user is provided with anindication of the computer's interpretation of the user's selection. Ifthe user desires to have the window 722 zoomed back to the back plane44, a user simply releases the selection mechanism of the cursor controlwhile the direction arrow 730 is pointing in the direction of the zoomback position. Upon release of the selection mechanism of the cursorcontrol, the window 722 is transformed or zoomed back to the back planeposition as illustrated in FIG. 7B.

Similar to the method by which the window 722 is positioned on the backplane 44, the user may zoom forward or transform the zoomed back window722 of FIG. 7C by positioning of the cursor 23 on the title bar 725 andthen clicking and dragging the cursor 23 upwards to produce thetwo-angled direction lines 734. The direction lines 734 indicates thatthe computer interprets the user's selection as a desired transformationto the front plane 38. If the user accepts this interpretation by thecomputer, the user releases the selection mechanism of the cursorcontrol which then causes the window 722 to zoom forward or fling to thefront plane position as illustrated in FIG. 7D.

Referring to FIGS. 8A and 8B, the control method for positioning awindow 822 on the right plane 56 using the window transform button 710is shown. In FIG. 8A, a cursor 23 is positioned on the window transformbutton 710, and the user clicks and drags the cursor toward the rightplane 38. When a user clicks and drags the cursor 23 towards the rightplane 38 while the cursor 23 is positioned on the window transformbutton 710, a plane direction arrow 830 points towards the right plane56. As discussed above, if the user desires to indicate or accept thecomputer's interpretation of the user's selection as indicated by thedirection arrow 830, the user simply releases the selection mechanism ofthe cursor control, and the window 822 is positioned on the right plane56 as illustrated in FIG. 8B. Referring to FIG. 8C, the method by whicha user repositions the window 822 on the front plane 38 is illustrated.In order to reposition the window 822 on the front plane 38, the userclicks on the window transform button 710 and releases the selectionmechanism of the control mouse. Upon release of the selection mechanismof the cursor control, the window 822 is repositioned on the front plane38 as illustrated in FIG. 8D. A direction arrow is not displayed whenthe window is transformed from a perspective view. As discussed above inconnection with FIGS. 4A-6C, the last plane information is saved.

Referring to FIGS. 9A and 9B, the control method for positioning awindow 922 on the left plane 50 using the window transform button 710 isshown. In FIG. 9A, a cursor 23 is positioned on the window transformbutton 710, and the user clicks and drags the cursor toward the leftplane 50. When a user clicks and drags the cursor 23 towards the leftplane 50, while the cursor 23 is positioned on the window transformbutton 710, a plane direction arrow 930 points towards the left plane50. As discussed above, if the user desires to indicate or accept thecomputer's interpretation of the user's selection as indicated by thedirection arrow 930, the user simply releases the selection mechanism ofthe cursor control, and the window 922 is positioned on the left planeas illustrated in FIG. 9B. The method by which a user repositions thewindow 922 on the front plane 38 is accomplished in the same mannerdiscussed in connection with FIGS. 8C and 8D.

Referring to FIGS. 10A and 10B, the control method for positioning awindow 1022 on the bottom plane using the window transform button 710 isshown. In FIG. 10A, a cursor 23 is positioned on the window transformbutton 710, and the user clicks and drags the cursor toward the bottomplane 106. When a user clicks and drags the cursor 23 towards the bottomplane 106, while the cursor 23 is positioned on the window transformbutton 710, a plane direction arrow 1030 points towards the bottom plane1030. As discussed above, if the user desires to indicate or accept thecomputer's interpretation of the user's selection as indicated by thedirection arrow 1030, the user simply releases the selection mechanismof the cursor control, and the window 1022 is positioned on the bottomplane 106 as illustrated in FIG. 10B. The method by which a userrepositions the window 1022 on the front plane 38 is accomplished in thesame manner discussed in connection with FIGS. 10C and 10D.

Planes and Boundaries for Three-Dimensional Windows

As noted above, window information is scaled and confined to certainareas on the display screen. Referring to FIG. 11, a system for definingthe perspective transform based environment and for providing anddefining the positions in which a window may be displayed isillustrated. A virtual isometric space system 80 provides a right planequadrilateral 84, left plane quadrilateral 88, and back plane and frontplane rectangles 92 and 96, respectively. The quadrilaterals andrectangles form the borders of a rectangular-prism or polyhedralisometric workspace. It should be appreciated that more or less complexsurfaces may be used. The boundaries defining the rectangles orquadrilaterals are consistent with the predefined isometric space. Thewalls, ceiling and floor may be explicitly displayed on the displayscreen at the user's option. The plane based system constrains windowshapes and sizes to the shape and sizes of the defined polygons. In thisexample, two walls, the right plane quadrilateral 84 and the left planequadrilateral 88, and two depth planes, the front and back planerectangles 92 and 96, respectively, define the three-dimensional spaceoperative to display windows. It should be noted that the top and bottomplanes 102 and 106 could also be used to display and transform windows.It should be appreciated three-dimensional workspaces may be createdthat are non-planer as discussed below.

The planes and geometry shown in FIG. 11 may be provided as the defaultgeometry for the graphical interface 12. The system may provide the userwith options to increase the depths and angles at which the basicgeometry of the isometric workspace is defined. Preferably, the linesand shapes defining the boundaries of the three-dimensional workspaceare not normally visible to the user, but during user customization, thelines demarcating the isometric space are made visible to the user. Asnoted above, the defined planes serve as a limit to the area in which auser may move a window on a particular plane or wall. For windowslocated in the perspective views or planes, the windows and text of thewindows become smaller as the text approaches the line or point definedalong the back edge of the plane. Generally, the point where objectsappear smaller as the objects are positioned closer to the point istermed the vanishing point. The vanishing point may be defined in memoryfor the display system. As illustrated, the window 1110 may not extendor be placed above the upper edge 120 of the right plane quadrilateral84. Similarly, the window 712 may not be positioned below the lower edge122 of the right plane quadrilateral 84. The present invention may beimplementing in a manner that reflects the depth of any object as afunction of the objects location in the defined isometric room orthree-dimensional workspace.

It should be appreciated by those skilled in the art that the userviewpoint of the windows may be changed. Changing the user's viewpointmay be accomplished by changing the defined depth of the user relativeto the windows (in the z-direction). Thus, moving the virtual locationof the user from "in front" of the planes workspace, and moving the userinto the workspace, allows the system to be used as an immersiveinterface with standard head tracking as used with a head mounteddisplay.

As known to those skilled in the art, a display screen may be dividedinto m by n elements generally known as pixels. A portion of thecomputer memory 20 is organized as a rectangular array of elements torepresent the pixels of the display screen. The pixels as defined by thecomputer memory 20 may be addressed in terms of Cartesian coordinates(x, y) corresponding to each pixel. More specifically, for the planes,the computer system may store a set of Cartesian coordinates whichidentify the memory area for the planes. Those skilled in the art willappreciate that the boundaries defining the isometric room 80 can bereadily established to provide the desired dimensions.

As discussed above, the display screen 15 may be divided into m by nelements which are organized as rectangular array of elements incomputer memory 20 and addressed in terms of (x, y) coordinates. Thus,lines or points defining the isometric room may be selected based on the(x, y) coordinates of the picture elements as represented in memory 20.When the desired points, lines, or shapes are selected for creating theplanes, the location of the memory elements which correspond to theselected boundaries of the planes in (x, y) coordinates of the displaybuffer can be stored. The stored boundaries may be then referenced inexecution of the steps of the present invention in order to providedefining or constraining regions for which a window located on a planemay be displayed. Well known methods of referencing a window being movedwithin the constraining boundaries of a display may be implemented tolimit the movement of windows within the defined isometric spaceboundaries. The isometric room is defined as a set ofperspective-transform objects. An isometric room is constructed bycreating four objects of the class "perspective-transform". A firstperspective-transform object's rotation is set to 90 degrees. The firstperspective-transform object now has the transformation information forthe left perspective-transform. A second perspective-transform object'srotation is set to -90 degrees. The second perspective-transform objectalso has it origin transformed so that it becomes the rightperspective-transform. A third perspective-transform object has itsorigin set so that it becomes the back perspective-transform. The fourthperspective-transform object has no modifications to its origin orrotation and is thus the front perspective-transform. The size of eachperspective-transform is a function of the display resolution that isused on the display monitor.

Windows are constrained to a perspective-transform by code in the windowclass that checks the coordinates of the window against the coordinatesof the containing perspective-transform. If an attempt is made to moveor size a window beyond these boundaries, the window adjusts thecoordinates to be within the boundaries of the containingperspective-transform.

The front and back perspective-transform share x and y coordinates. Theleft and right perspective-transforms have a different x, y position foreach perspective-transform. By using different x, y positions for theleft and right perspective-transforms, the user can position a windowcloser when on left perspective-transform than when it is on the rightperspective transform. This x, y coordinate information is stored inseparate member variables within the window class. This coordinateinformation can be within the perspective-transform itself and thus awindow would not directly know where it is located in two-dimensionalspace. The window would only have information stored about its width andheight. As those skilled in the art will understand, the stacking oroverlaying of windows in the three-dimensional environment of thepresent invention is generally handled in the same manner as aconventional window display environment. However, as noted herein, awindow is placed, in the z-position, in the first available slot of az-order list of the perspective-transform selected. With the presentinvention, windows on the front perspective-transform 38 remain fullyvisible on the display screen when the window on the frontperspective-transform 38 intersects data from a window displayed on aside perspective transform.

Referring to FIG. 12, a non-planar bounding surface 141 for definingthree-dimensional depth perception is shown. The bounding surface 141 isdefined as a half sphere whose rim 143 meets the front bounding plane147. Windows 151, 153, and 157 are shown transformed to conform to theshape defined by the bounding surface 141. The windows 151, 153, and 155are transformed to their respective shapes with transformation matricesaccording to the window position defined by the bounding surface 141.Those skilled in the art will appreciate that many other shapes ofbounding surfaces may be defined for use as a bounding surface toprovide three-dimensional graphics to a window based user interface.

Multiple Three-Dimensional/Isometric Workspaces

Referring to FIG. 13, another system for defining theperspective-transforms based environment and for providing and definingthe positions in which a window may be displayed is illustrated. Avirtual isometric space system 160 defines multiple isometric spaces161, 163, 165, and 167. Separating boundary planes 171, 173, 175, and177 separate the multiple isometric spaces 161, 163, 165, and 167. Theseparating boundary planes 171, 173, 175 and 177 intersect a non-planarbounding surface 180. The non-planar bounding surface 180 is cylindricalin shape. It should be appreciated that the non-planar bounding surfacemay vary in shape. Each isometric space 161, 163, 165, and 167 maycontain a set of planes and windows at various positions andconfigurations, consistent with their position in each isometric space,as discussed above with the single isometric space. A user can view asingle space at a time such as the single space 161. A user can accessthe space directly by placing the cursor 23 in a selected isometricspace and providing a selection single when the cursor is positioned inthe selected space. Alternatively, the user can rotate to a selectedisometric space by selecting isometric space selection controls 181 or183. The isometric space selection controls 181 and 183 operate torotate through the isometric space as indicated by an arrow on thecontrols. It should be appreciated that animation effects may bedisplayed during transitions between the isometric spaces 161, 163, 165,and 167. Referring to FIG. 14, a global view of the isometric spacesystem 160 is shown in the upper right hand corner of FIG. 14. Thewindows in the foreground of FIG. 14 is the isometric space 161.

Cursor Operation

As discussed above, the computer system of the preferred embodiment ofthe present invention provides depth cues to the windows. As alsodiscussed above, a cursor is used to designate or select certain controlitems within the preferred embodiment of the present invention. Tofurther enhance the depth cues of the display system utilized with thepresent invention, the computer system of the present inventiondynamically sizes the cursor according to the window on which the cursoris positioned and/or the position of the cursor on a window. The cursorsize reflects the depth of the location of the cursor in the definedisometric space. The preferred embodiment of the present inventionconsiders a location of the cursor to be on the surface of the planeoccupied by the window, whether the cursor is positioned in a normal,nonperspective transformed window, a perspective transformed window, ora zoomed out window.

Referring to FIG. 15, the dynamic cursor sizing operation of thepreferred embodiment of the present invention is illustrated. Thecomputer system of the present invention dynamically sizes the cursor 23by automatically changing the size of the cursor 23 when the cursor 23moves along a transformed window, "toward" or "away" from the user, whenthe cursor moves across a window border to another window, or when thecursor moves from a window to a non-window area of the display screen.The computer 16 (FIGS. 1 and 2) determines the location of the cursor 23on the display screen 15 as known to those skilled in the art, thenresizes the cursor 23 to a predetermined size for the cursor 23 based onthe particular location of the cursor on the display screen 15 and/orbased on whether the cursor is positioned on a window at the cursorlocation. The cursor 23 is at its largest when it is not positioned on awindow. Although multiple cursors 23 are illustrated in FIG. 15, thoseskilled in the art should appreciate that generally only one cursor isdisplayed at a time. The multiple cursors 23 illustrated in FIG. 15represent different positions 1510 of the cursor 23 on the displayscreen 15.

For example, the dynamic sizing of the cursor 23 may occur as follows.The cursor 23 at position 1510(a) is considered to be "not positioned ona window". When a cursor 23 is moved from position 1510(a) to position1510(e) on the nontransformed window 1522, the computer system reducesthe size of the cursor 23 at position 1510(e) as compared to the cursorposition 1510(a) which is not on a window. By reducing the size of thecursor 23, the computer system indicates that the position of the cursor23 is further back in the display system. When the cursor 23 is movedfrom position 1510(e) to either position 1510(b) or 1510(c) on thezoomed back window 1532 the cursor 23 becomes even smaller. When acursor 23 is positioned on a window or plane that is perpendicular tothe user's view or appears straight ahead in the user's line of view,the cursor size within the window that is perpendicular to the user'sview remains the same. For example, the size of the cursor 23 located atposition 1510(e) and the size of the cursor 23 at 1510(f) are the same.The size of the cursor 23 located at positions 1510(a) and 1510(d) whichare not positioned on a window or positioned in an open space are thesame. The open space is considered to be perpendicular to the user'sline of view. Also, as indicated at positions 1510(b) and 1510(c), thecursor's size is the same along the zoomed back view of window 1532Generally when the cursor is located at the same z-position along aperspective transform or plane as determined by the computer, the cursorsize appears to be the same on the display screen 15.

As noted above, the size of the cursor 23 automatically changes when itcrosses from and to objects located on different planes. By changing thesize of the cursor 23 as it passes across the border 1524 of window 1522along the path 1530, the cursor 23 appears to snap to, jump to, or moveto a different plane. Similarly, when the cursor 23 moves from position1510(d) and across the border 1534 of window 1532 along the path 1531,the cursor appears to snap to the window 1532 when it decreases in sizeas illustrated at position 1510(c). The size of a cursor automaticallysnaps to or resizes when the cursor 23 crosses the border of a window toanother window or open space to indicate another depth level defined inthe display system of the computer system.

Similar to the dynamic resizing of the cursor 23 as it crosses theborder of a window to a different window or to open space, the cursor 23is dynamically resized as the cursor 23 is moved along a perspectivetransformed window in the z-direction. When the cursor 23 is moved onperspective transformed windows, such as window 1542, the size of thecursor 23 is dictated by the position of the cursor 23 and the locationof the window. When the cursor 23 is moved "away" from the user such asalong the z axis in FIG. 15, the size of the cursor 23 decreases. Forexample, the size of the cursor 23 on the window 1542 at position1510(h) is larger than the size of the cursor 23 located at position1510(i). Further, the size of cursor 23 located at position 1510(j) issmaller than the sizes of the cursor 23 located at positions 1510(i),1510(g), and 1510(h) on the window 1542. Thus, in accordance with amethod of the present invention the size of the cursor 23 decreases inthe direction away from the user.

In addition to the resizing as discussed above, the speed or animationof cursor transitions between windows at different depths may varydepending on the relative distance between transitions between windows.A cursor transition between windows can be considered an animated jump.The animated jump may be characteristically different when jumping upfrom a more distance window in the three-dimensional space than whenjumping down from a window that is closer to the user. Animated jumps ofthe cursor may also have a characteristic sound associated withtransitions of various distances or depths in the three-dimensionalspace.

Object-Oriented Programming for Three-Dimensional Windows

As noted above, window display systems preferably are implemented withobject-oriented programming, Preferably, classes are implemented for allof the major functional pieces of the interface. Application programminginterfaces (API's) that provide three-dimensional transforms arepreferably used. The following description discusses the implementationof objects used with the present invention and how the different objectsinteract with each other. The following is a description of the classesthat are utilized with the present invention.

With respect to the interface, the basic building block is preferably agroup. A group consists of a right and left perspective transform aswell as a front and back perspective transform. As discussed herein,only one group is utilized, but this is an implementation detail and nota limitation of the system. Multiple groups may be used. Groups have novisible portions. Groups only affect the location of the perspectivetransforms that make up the group.

Perspective transforms, as discussed herein, are generally an invisiblepart of the interface that affect the display of windows that areattached along the predefined boundaries of the computer screenworkspace. Perspective transforms apply any existing transformationinformation to the drawing context before requesting all containedobjects to draw themselves into the drawing context. When the scene isrendered, the group object notifies each perspective transform object inturn to render itself through the user of a draw function. Internallythis draw function makes a set of calls to set the currenttransformation matrix to the desired matrix. For example, the leftperspective transform sets the matrix so that all drawing commands arerotated 90 degrees counter clockwise so that a line being drawn fromleft to right will appear to go away from the observer into the screen.After the perspective transform object has set the transformation matrixit then calls the draw function for each of its contained objects.Normally these objects are window objects that only know how to draw intwo dimensions. Because the transformation matrix has rotated everythingthe window will appear to draw in three dimensions. Also the perspectivetransform object will adjust the transformation matrix after eachcontained object has been drawn so that the objects appear stacked ontop of each other. Perspective transforms also utilize a z-orderstacking as discussed above to make sure that all of the containedwindows are drawn without overlapping visualizations.

As noted above, the operating system of the present invention useswindows extensively as part of the display system. Windows generallyonly have graphical information about their location in two-dimensionalspace (even though the underlying object class stores origin informationfor x, y, and z coordinates) and some state information necessary forproper restoration from a perspective transformed position. A window mayneed to store state information about the last perspective transform towhich the window was attached so that the window can be returned to theappropriate perspective transform when the same perspective-transformbutton is selected twice. For example, if a window is currently on thefront perspective transform, and the perspective-transform left buttonis selected, the window will be moved to the left perspective transform.The window stores an indication that it is leaving the front perspectivetransform so if the perspective transform left button is selected againthe window can be attached to the front perspective transform again. Theinformation about a window's two-dimensional location could all bestored at the perspective transform level with a dictionary using thewindow object as the key and storing the two-dimensional location of thewindow on the perspective transform as the value. When a window isremoved from either the front or back perspective transform, theperspective transform is saved so that the window can be reattached whenone of the other positioning controls is activated. The windows displaythemselves in response to requests from the owning perspectivetransform. Windows also request the controls that are contained to drawthemselves.

A client area class is used to represent the client area of a window.The client area is where an application performs its drawing. The API'sare used to implement the drawing and use display lists to optimize thedrawing. Display lists provide a technique of preprocessing a sequenceof drawing instructions and then referencing during the instructionsthrough an integer identification. All visible components of theinterface have an associated display list. In the case of the controls(system menu, title bar, pushback, perspective-transform left andperspective-transform right) a single display list is used that is astatic member of the respective class. All windows have a display listfor their border and all client area instances use a display list tostore the drawing code necessary for displaying themselves.

In order to optimize the drawing code when an object is in motion, atechnique known as "scissoring" is used. This technique involves findingthe minimum rectangular region of pixels that need to be refreshed andlimiting the drawing to that set of pixels. Scissoring is a general namefor a technique of clipping the drawing to a specific set of pixels.Scissoring is also known as marking.

Display Processing Steps

The preferred steps of the method for displaying or simulating athree-dimensional operating system are shown in FIGS. 16a and 16b. Asnoted above, information for displaying a window is received from acomputer application and is displayed by manipulating conventionalrectangular coordinate information to redraw the data on the computerscreen using selected depth cues. The steps of the preferred method areimplemented with a computer program operating on a general purposecomputer such as the computer system 10 in FIG. 1. It will beappreciated that conventional software development techniques are usedfor developing the computer program implemented in conjunction with thepresent invention. The preferred steps will be discussed in conjunctionwith FIGS. 1 and 2.

Referring to FIGS. 1, 2, and 16a, the processes implemented inconjunction with the present invention are shown. At step 1602, thecomputer system 10 is powered up, and the operating system of thepresent invention is booted at step 1604. At step 1606, a computer usermay invoke an application, or a routine specified during the system bootprocedure may invoke an application. When an application is invoked, atstep 1608, the window display system of the present invention displaysthe application data on the front perspective transform. At step 1612,the CPU 22 waits for a command from a computer user. When a command isreceived at the CPU 22, the process proceeds to step 1620. At step 1620,a determination is made as to whether the user command was a windowtransformation control or standard user command. If the command enteredwas a standard command, the display screen 15 is updated, at step 1626,by the CPU 22 according to the standard command. The process thenproceeds to step 1612 to await another user command. If, however, atstep 1612, the user selected a window transformation command, such asPush back 64, perspective-transform left 66, or perspective-transformright 68, the process proceeds to step 1624 where the appropriate windowtransformation is implemented.

Referring additionally to FIG. 16b, the discussion of the preferredprocesses of the present invention is continued. At step 1702, theappropriate window data is accessed as discussed above. At step 1710,the CPU 22 determines whether the transformation command was a push back(zoom back) 64, perspective-transform left (PL) 66, orperspective-transform right (PR) 68 command. If the command was a pushback 64 command, the process proceeds to step 1714 where the appropriatezoom function is implemented as discussed above. If the command was aperspective-transform right 66 command, the process proceeds to step1712 where the perspective-transform right function is implemented asdiscussed above. If the command was a perspective-transform left 66command, the process proceeds to step 1716 where theperspective-transform left function is implemented as discussed above.

In summary, the preferred embodiment of the present invention provides athree-dimensional virtual workspace for window based display systems.The display system of the present invention is an isometric displaysystem for an operating system. The isometric display system provides adisplay with monocular depth cues by making automatic sizing andgeometric transformations on two dimensional rectangles that definetraditional windows.

The isometric display system performs geometric transformationoperations on rectangular windows to convey the impression to the userthat the windows are positioned in a three-dimensional space. Theimpression of depth and of working in a three-dimensional space arecreated by transforming two-dimensional windows to appear as if thetwo-dimensional windows are embedded at orientations and positions in athree-dimensional isomeric space. The isometric display system respondsto user activation of control buttons by transforming the shape andorientation of windows consistent with the defined three-dimensionalspace.

The preferred embodiment of the present invention provides left, right,front, and back planes or perspective transforms within the displaysystem that operate to display an application or window on a userselected plane. The planes are preferably organized or defined as thewalls of a four-sided room as seen when viewing the room from theoutside. The planes defining the three-dimensional room or space areshaped to provide depth perception within the display monitor. The leftand right planes narrow in dimension as viewed from the front to back ofthe space defined on the display screen. Additionally, the front planeappears closer to the user than the back plane. The planes arepreferably not visible but when a plane is selected by a user to displaya window, the window's shape and contents are transformed or rescaled toconform to the shape of the planes. The simulated depth perception iscreated by transforming designated windows so that they conform to thedimensions of the respective plane or position on which the window isdesignated for display. The contents of displayed windows may begenerally viewed in full when the windows are hung on different planes.

The foregoing relates to the preferred embodiment of the presentinvention, and many changes may be made therein without departing fromthe scope of the invention as defined by the following claims.

We claim:
 1. In a computer system operative to display computerapplication data in a window on a display monitor, said window havingsides defining a geometrical shape and defining an enclosed area forpresenting said data on said display monitor, said computer systemcharacterized by resources including a central processing unit (CPU), amemory, and display monitor said resources communicating via a systembus, said CPU operative to control processes for defining the size andshape of displayed windows, a method for resizing sides defining thearea of the window, comprising the steps of:displaying a first window onsaid display monitor; receiving a control signal at said CPU forreshaping the boundaries defining the geometrical shape of said window;and responsive to receiving said control signal at said CPU, decreasingthe dimensions of a displayed boundary of said first window relative tothe opposite side of said first window, thereby yielding athree-dimensional transformed window having different dimensions thansaid first window and having a different geometrical shape than saidfirst window.
 2. The method of claim 1 wherein said opposite side is theright side of said first window.
 3. The method of claim 2 furthercomprising displaying a first set of data within said first window anddecreasing the size of said first set of data as displayed from the leftside to the right side of said area defined by said boundaries of saidfirst window, thereby defining a scaled set of data for display withinsaid transformed window.
 4. The method of claim 3 wherein said step ofdecreasing the size of said first set of data is scaled to correspond tothe scale of the decreasing sides of said transformed window.
 5. Themethod of claim 1 wherein said opposite side is the left side of saidfirst window.
 6. The method of claim 5 further comprising displaying afirst set of data within said first window and decreasing the size ofsaid first set of data as displayed from right side of the area definedby said boundaries of said first window to the left side of said areadefined by said boundaries of said first window, thereby defining ascaled set of data for display within said transformed window.
 7. Themethod of claim 6 wherein said step of decreasing the size of said firstset of data is scaled to correspond to the scale of the decreasing sidesof said transformed window.
 8. In a computer system operative to displaycomputer application data in a window on a display monitor, said windowshaving sides defining an enclosed area for presenting said data on saiddisplay monitor, said computer system characterized by resourcesincluding a central processing unit (CPU), a memory, and display monitorsaid resources communicating via a system bus, said CPU operative tocontrol processes for defining the size and shape of displayed windows,a method for resizing sides defining the area of the window, comprisingthe steps of:displaying said window on said display monitor, said windowcontaining data symbols; receiving a control signal at said CPU forresealing the boundaries defining the geometrical shape of said window;and responsive to receiving said control signal at said CPU, rescalingthe size of the displayed boundaries of said window and rescaling thesize of data symbols contained in said window, thereby yielding athree-dimensional transformed window having different dimensions thansaid window and containing rescaled data symbols.
 9. The method of claim8 wherein said step of resealing comprises scaling said transformedwindow to back to the same geometric shape of said window.
 10. Themethod of claim 8 further comprising providing a control button for saidwindow operative to scale said window and said symbols of said window toa first or second size upon selection of said control button.
 11. Themethod of claim 8 wherein said step of resealing comprises multiplyingthe boundaries and data of said window by a transformation matrix toyield said transformed window.
 12. In a computer system operative todisplay computer application data in a window on a display monitor, saidwindows having boundaries defining a geometrical shape and an enclosedarea for presenting said data on said display monitor, said computersystem characterized by resources including a central processing unit(CPU), a memory, and display monitor said resources communicating via asystem bus, said CPU operative to control processes for defining thesize and shape of displayed windows, a method for resizing sidesdefining the area of the window, comprising the steps of:displaying aplurality of windows on said display monitor; receiving a control signalat said CPU for rescaling the boundaries defining the geometrical shapeof at least one of said windows; and manipulating, via said CPU, theboundaries and data of at least one of said windows to providethree-dimensional depth cues to said boundaries and data of saidwindows, thereby yielding at least one three-dimensional transformedwindow having different boundaries than another one of said windows andcontaining rescale data.
 13. The method of claim 12 wherein said step ofmanipulating the boundaries and data comprises decreasing the dimensionsof a displayed boundary of a first window relative to a oppositeboundary of said first window thereby yielding a transformed firstwindow and displaying said transformed first window on a first side ofsaid display screen.
 14. The method of claim 13 wherein said step ofmanipulating the boundaries and data of said windows comprisesdecreasing the dimensions of a displayed boundary of a second windowrelative to a opposite boundary of said second window thereby yielding atransformed second window of different dimensions than said secondwindow and having a different geometrical shape than said second windowand displaying said transformed second window on a second side of saiddisplay screen.
 15. The system of claim 14 wherein said first and secondsides are located on opposite sides of the display screen of saiddisplay monitor.
 16. The system of claim 15 wherein said first side islocated on the left side of said display screen and said second side islocated on the right side of said display screen.
 17. The system ofclaim 15 wherein said first side is located at the top of said displayscreen and said second side is located at the bottom of the displayscreen.
 18. The method of claim 13 wherein said step of manipulating theboundaries and data of said windows comprises decreasing the dimensionsof a displayed boundary of a third window relative to a oppositeboundary of said third window thereby yielding a transformed thirdwindow of different dimensions than said third window and having adifferent geometrical shape than said third window and displaying saidtransformed third window on a third side of said display screen.
 19. Themethod of claim 18 wherein said step of manipulating the boundaries anddata of said windows comprises decreasing the dimensions of a displayedboundary of a fourth window relative to a opposite boundary of saidfourth window thereby yielding a transformed fourth window of differentdimensions than said fourth window and having a different geometricalshape than said fourth window and displaying said transformed fourthwindow on a fourth side of said display screen.
 20. The system of claim19 wherein said third and fourth sides are located on opposite sides ofthe display screen of said display monitor.
 21. In a computer systemoperative to display computer application data in a window on a displayscreen of a display monitor, said windows having sides defining anenclosed area for presenting said data on said display monitor, saidcomputer system characterized by resources including a centralprocessing unit (CPU), a memory, and display monitor said resourcescommunicating via a system bus, said CPU operative to control processesfor defining the size and shape of displayed windows, a method forresizing sides defining the area of the window, comprising the stepsof:providing a plurality of window transformation controls for saidcomputer system; displaying a plurality of windows on said displayscreen of said display monitor; selecting a location in said memoryrepresentative of a selected point on said display screen; and uponselection of said transformation control, scaling the data anddimensions of one of said windows appearing closer to said selectedpoint of said display monitor to a size smaller than the dimensions anddata appearing farther from the selected point of said display screen,thereby yielding a three-dimensional transformed window having differentdimensions than one of said windows appearing farther from the selectedpoint of said display screen.
 22. The method of claim 21 wherein saidstep of selecting comprises selecting a point representative of thecenter of said display screen.
 23. In a computer system having anoperating system operative to display computer application data in awindow on a display monitor having a display screen, said windows havingborders defining an enclosed area for presenting said data on saiddisplay monitor, a method of managing data displayed on said displaymonitor, comprising:partitioning, via said operating system, the displayscreen of said display monitor into a plurality of preselectedboundaries; providing three-dimensional visual depth cues correspondingto said preselected boundaries, said visual depth cues indicating theposition and orientation of selected windows displayed by said operatingsystem; and manipulating said preselected boundaries for one of saidselected windows to present a three-dimensional transformed windowhaving different boundaries than another one of said selected windows.24. The method of claim 23 wherein said step of partitioning comprisespartitioning said display screen into an isometric room for providingvisual depth cues.
 25. The method of claim 24 further comprisingproviding visual depth cues to objects displayed on said display screen.26. The method of claim 24 further comprising displaying a cursor andproviding visual depth cues indicative of the location of said cursor insaid isometric room.
 27. The method of claim 24 further comprisingdisplaying said preselected boundaries aid display screen.
 28. Themethod of claim 24 further comprising displaying the boundaries definingsaid isometric room.
 29. In a computer system having an operating systemoperative to display computer application data in windows on a displayscreen of a display monitor, said windows having borders defining anenclosed area for presenting said data on said display monitor, saidcomputer system characterized by resources including a centralprocessing unit (CPU), a memory, and display monitor said resourcescommunicating via a system bus, said CPU operative to control processesfor defining the size and shape of displayed windows, a method forindicating the destination of a window to be redefined, comprising thesteps of:displaying a window of information on said display screen;providing a transformation control on said display screen fortransforming said window of said operating system to a predefined plane,said transformation control operative to provide depth cues to saidwindow; and upon selection of said transformation control, providing apointer to said predefined plane and presenting a three-dimensionaltransformed window having different dimensions than said window andcontaining rescaled data.
 30. The method of claim 29 wherein said stepof providing said pointer comprises providing a pointer that isoperative to point to a plurality of predefined planes.
 31. The methodof claim 30 wherein said pointer comprises a direction arrow.
 32. Themethod of claim 31 wherein said selection of said transformation controlcomprises guiding a cursor to said transformation control and providinga selection signal from a cursor control while said cursor is guided inthe direction of said predefined plane.
 33. In a computer system havinga visual display screen, a computer-implemented method of providing asimulated three-dimensional virtual workspace interface for an operatingsystem based on windows, each of said windows being defined by bordersand having data displayed therein, comprising:partitioning, via saidoperating system, the display screen of said display monitor into aplurality of planes; and narrowing the dimensions defining certain onesof said planes from the front of said display screen to the rear of saiddisplay screen, each of said dimensions operative to provide depthperception to windows selected for display on said certain planes,thereby yielding at least one three-dimensional transformed windowhaving different dimensions than another one of said windows.
 34. Themethod of claim 33 wherein said step of narrowing the dimensionsdefining each of said planes comprises narrowing the dimensions of aplane located on the left side of said display screen and narrowing thedimensions of a plane located on the right side of said display screen.35. In a computer system having a display system, said visual displaysystem operating in conjunction with a visual display screen, acomputer-implemented method of providing a simulated three-dimensionalvirtual workspace interface for an operating system based on windows,each of said windows being defined by borders and having data displayedtherein, comprising:partitioning, via said operating system, the displayscreen of said display monitor into a plurality of first planes, atleast one of said first planes operative to provide three dimensionaldepth perception to a window selected for display on said at least oneof said first planes; and defining an adjacent plane adjacent to said atleast one of said first planes, said adjacent plane being positioned aselected increment away from said at least one of said first planesalong the normal vector from said at least one of said first planestowards the center of said virtual workspace, said adjacent planeoperative to provide three-dimensional depth perception to a windowselected for display on said adjacent plane.
 36. The method of claim 35further comprising the step of defining a plurality of said adjacentplanes; and wherein said visual display system is operative to display awindow on one of said adjacent planes when a window is displayed on saidat least one of said first planes.
 37. The method of claim 36 furthercomprising the step of displaying a window on the adjacent plane closestto said at least one of said first planes.
 38. In a computer systemhaving a visual display system, a computer-implemented method ofproviding a simulated three-dimensional virtual workspace interface foran operating system based on windows, each of said windows being definedby borders and having data displayed therein, comprising:defining afirst set of display surfaces in said visual display system, said firstset of display surfaces operative to define a first three-dimensionalvirtual workspace; and providing three-dimensional depth cues to atleast one of said windows upon selection of said one of said displaysurfaces of said first set to present a three-dimensional transformedwindow having different dimensions than another one of said windows. 39.The method of claim 38 further comprising the steps of:defining a secondset of display surfaces in said visual display system, said second setof display surfaces operative to define a second three-dimensionalvirtual workspace; and providing three-dimensional depth cues to atleast one of said windows upon selection of said one of said displaysurfaces of said second set of said display surfaces.
 40. The method ofclaim 39 further comprising the step of providing a control forselecting said first or said second three dimensional virtual workspacefor use.
 41. The method of claim 38 further comprising the step ofvarying the level of sound that emanates from said computer system basedon the location of selected window upon which a user is operating. 42.The method of claim 41 wherein said step of varying the level of soundcomprises generating said sound from a direction that causes said soundto appear to emanate from the direction of said selected window.